Field of the Invention
The present invention relates to a surface mounted light emitting apparatus used in illumination apparatus, display, backlight for mobile phone, auxiliary light source for illumination or other light source for consumer electric apparatus, a resin molding suitable for the surface mounted light emitting apparatus and methods for manufacturing both.
Description of the Related Art
A surface mounted light emitting apparatus which employs a light emitting device is compact, has high power efficiency and emits light of clear color. The light emitting device is also free from burnout, because it is a semiconductor device. It also has an excellent initial drive characteristic, and high durability against vibration and repetitive cycles of turning on and off. Because of such excellent characteristics, light emitting apparatuses which use light emitting devices such as light emitting diode (LED) or laser diode (LD) are used as various light sources.
FIG. 11 shows a surface mounted light emitting apparatus of the prior art. The surface mounted light emitting apparatus of the prior art comprises a light emitting device 210, a lead frame for mounting 220 for mounting the former thereon, a lead frame for connection 230 which is connected to the light emitting device 210 via leads, and a molding 240 which covers most of the lead frames (refer to, for example, Japanese Unexamined Patent Publication (Kokai) No. 11-087780 (claims, paragraph [0020])). In the surface mounted light emitting apparatus, the molding 240 is often formed from a light blocking resin such as liquid crystal polymer, PPS (polyphenyl sulfide) or nylon which is a thermoplastic resin for the reason of convenience in mass production. Also because the thermoplastic resin used in the molding 240 is required to have enough heat resistance to endure the heat of reflow soldering, engineering polymers such as polyphthalamide, liquid crystal polymer and PPS are used. The thermoplastic resin is formed by injection molding process. The injection molding process is employed in preference for the reason of high productivity thereof, in the manufacture of the surface mounted light emitting apparatus which has high output power at a low cost.
The thermoplastic engineering plastics as mentioned above used in forming the molding 240 for the surface mounted light emitting apparatus of the prior art have high heat resistance, although contains an aromatic component in the molecule and therefore have low resistance to light. Also because these materials do not have hydroxide group which improves adhesive property at the end of the molecule, sufficient bonding cannot be achieved between the lead frames 220, 230 and the translucent encapsulant resin 250. Moreover, as the light emitting devices are produced with rapidly increasing output power in recent years, the problem of light degradation of the molding 240 is becoming more conspicuous. Bonding between the translucent encapsulant resin 250 and the thermoplastic engineering polymer 240, in particular, can be easily destroyed due in part to the weak bonding strength, thus resulting in delamination. Even when the delamination does not result, discoloration caused by light degradation proceeds and results in drastically short life of the light emitting device.
There is a technology proposed to solve these problems which forms the molding from an inorganic material that is free from light degradation, such as ceramics. However, the molding formed from ceramics makes it difficult to insert the lead frame which has high thermal conductivity, and therefore resistance to heat transfer cannot be decreased. Also because the thermal expansion coefficient is different from that of the translucent encapsulant resin by a factor of 10 or more, sufficient level of reliability has not been achieved.